如何为水平回收视图制作页面指示器

Question

知道如何为recyclerview列表创建页面指示器吗？

Answer 1

您可以使用RecyclerView.ItemDecoration添加指标.

只需在底部绘制一些线条或圆圈,然后使用它layoutManager.findFirstVisibleItemPosition()来获取当前活动项目.由于寻呼机倾向于填充整个宽度,因此这是获取显示项目的累积方式.这也允许我们通过比较孩子的左边缘和父母来计算滚动距离.

下面是一个样本装饰,它在它们之间绘制一些线条和动画

public class LinePagerIndicatorDecoration extends RecyclerView.ItemDecoration {

  private int colorActive = 0xFFFFFFFF;
  private int colorInactive = 0x66FFFFFF;

  private static final float DP = Resources.getSystem().getDisplayMetrics().density;

  /**
   * Height of the space the indicator takes up at the bottom of the view.
   */
  private final int mIndicatorHeight = (int) (DP * 16);

  /**
   * Indicator stroke width.
   */
  private final float mIndicatorStrokeWidth = DP * 2;

  /**
   * Indicator width.
   */
  private final float mIndicatorItemLength = DP * 16;
  /**
   * Padding between indicators.
   */
  private final float mIndicatorItemPadding = DP * 4;

  /**
   * Some more natural animation interpolation
   */
  private final Interpolator mInterpolator = new AccelerateDecelerateInterpolator();

  private final Paint mPaint = new Paint();

  public LinePagerIndicatorDecoration() {
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(mIndicatorStrokeWidth);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setAntiAlias(true);
  }

  @Override
  public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
    super.onDrawOver(c, parent, state);

    int itemCount = parent.getAdapter().getItemCount();

    // center horizontally, calculate width and subtract half from center
    float totalLength = mIndicatorItemLength * itemCount;
    float paddingBetweenItems = Math.max(0, itemCount - 1) * mIndicatorItemPadding;
    float indicatorTotalWidth = totalLength + paddingBetweenItems;
    float indicatorStartX = (parent.getWidth() - indicatorTotalWidth) / 2F;

    // center vertically in the allotted space
    float indicatorPosY = parent.getHeight() - mIndicatorHeight / 2F;

    drawInactiveIndicators(c, indicatorStartX, indicatorPosY, itemCount);


    // find active page (which should be highlighted)
    LinearLayoutManager layoutManager = (LinearLayoutManager) parent.getLayoutManager();
    int activePosition = layoutManager.findFirstVisibleItemPosition();
    if (activePosition == RecyclerView.NO_POSITION) {
      return;
    }

    // find offset of active page (if the user is scrolling)
    final View activeChild = layoutManager.findViewByPosition(activePosition);
    int left = activeChild.getLeft();
    int width = activeChild.getWidth();

    // on swipe the active item will be positioned from [-width, 0]
    // interpolate offset for smooth animation
    float progress = mInterpolator.getInterpolation(left * -1 / (float) width);

    drawHighlights(c, indicatorStartX, indicatorPosY, activePosition, progress, itemCount);
  }

  private void drawInactiveIndicators(Canvas c, float indicatorStartX, float indicatorPosY, int itemCount) {
    mPaint.setColor(colorInactive);

    // width of item indicator including padding
    final float itemWidth = mIndicatorItemLength + mIndicatorItemPadding;

    float start = indicatorStartX;
    for (int i = 0; i < itemCount; i++) {
      // draw the line for every item
      c.drawLine(start, indicatorPosY, start + mIndicatorItemLength, indicatorPosY, mPaint);
      start += itemWidth;
    }
  }

  private void drawHighlights(Canvas c, float indicatorStartX, float indicatorPosY,
                              int highlightPosition, float progress, int itemCount) {
    mPaint.setColor(colorActive);

    // width of item indicator including padding
    final float itemWidth = mIndicatorItemLength + mIndicatorItemPadding;

    if (progress == 0F) {
      // no swipe, draw a normal indicator
      float highlightStart = indicatorStartX + itemWidth * highlightPosition;
      c.drawLine(highlightStart, indicatorPosY,
          highlightStart + mIndicatorItemLength, indicatorPosY, mPaint);
    } else {
      float highlightStart = indicatorStartX + itemWidth * highlightPosition;
      // calculate partial highlight
      float partialLength = mIndicatorItemLength * progress;

      // draw the cut off highlight
      c.drawLine(highlightStart + partialLength, indicatorPosY,
          highlightStart + mIndicatorItemLength, indicatorPosY, mPaint);

      // draw the highlight overlapping to the next item as well
      if (highlightPosition < itemCount - 1) {
        highlightStart += itemWidth;
        c.drawLine(highlightStart, indicatorPosY,
            highlightStart + partialLength, indicatorPosY, mPaint);
      }
    }
  }

  @Override
  public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    super.getItemOffsets(outRect, view, parent, state);
    outRect.bottom = mIndicatorHeight;
  }
}

哪个会给你一个像下面这样的结果

还有一篇博文更详细地介绍了装饰如何在这里工作,完整的源代码可以在GitHub上找到

Answer 2

我更改了圆圈的代码.删除了绘制线的代码,并将其替换为绘制圆方法.请在下面找到完整的课程:

public class CirclePagerIndicatorDecoration extends RecyclerView.ItemDecoration {
    private int colorActive = 0xDE000000;
    private int colorInactive = 0x33000000;

    private static final float DP = Resources.getSystem().getDisplayMetrics().density;

    /**
     * Height of the space the indicator takes up at the bottom of the view.
     */
    private final int mIndicatorHeight = (int) (DP * 16);

    /**
     * Indicator stroke width.
     */
    private final float mIndicatorStrokeWidth = DP * 4;

    /**
     * Indicator width.
     */
    private final float mIndicatorItemLength = DP * 4;
    /**
     * Padding between indicators.
     */
    private final float mIndicatorItemPadding = DP * 8;

    /**
     * Some more natural animation interpolation
     */
    private final Interpolator mInterpolator = new AccelerateDecelerateInterpolator();

    private final Paint mPaint = new Paint();

    public CirclePagerIndicatorDecoration() {

        mPaint.setStrokeWidth(mIndicatorStrokeWidth);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setAntiAlias(true);
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDrawOver(c, parent, state);

        int itemCount = parent.getAdapter().getItemCount();

        // center horizontally, calculate width and subtract half from center
        float totalLength = mIndicatorItemLength * itemCount;
        float paddingBetweenItems = Math.max(0, itemCount - 1) * mIndicatorItemPadding;
        float indicatorTotalWidth = totalLength + paddingBetweenItems;
        float indicatorStartX = (parent.getWidth() - indicatorTotalWidth) / 2F;

        // center vertically in the allotted space
        float indicatorPosY = parent.getHeight() - mIndicatorHeight / 2F;

        drawInactiveIndicators(c, indicatorStartX, indicatorPosY, itemCount);

        // find active page (which should be highlighted)
        LinearLayoutManager layoutManager = (LinearLayoutManager) parent.getLayoutManager();
        int activePosition = layoutManager.findFirstVisibleItemPosition();
        if (activePosition == RecyclerView.NO_POSITION) {
            return;
        }

        // find offset of active page (if the user is scrolling)
        final View activeChild = layoutManager.findViewByPosition(activePosition);
        int left = activeChild.getLeft();
        int width = activeChild.getWidth();
        int right = activeChild.getRight();

        // on swipe the active item will be positioned from [-width, 0]
        // interpolate offset for smooth animation
        float progress = mInterpolator.getInterpolation(left * -1 / (float) width);

        drawHighlights(c, indicatorStartX, indicatorPosY, activePosition, progress);
    }

    private void drawInactiveIndicators(Canvas c, float indicatorStartX, float indicatorPosY, int itemCount) {
        mPaint.setColor(colorInactive);

        // width of item indicator including padding
        final float itemWidth = mIndicatorItemLength + mIndicatorItemPadding;

        float start = indicatorStartX;
        for (int i = 0; i < itemCount; i++) {

            c.drawCircle(start, indicatorPosY, mIndicatorItemLength / 2F, mPaint);

            start += itemWidth;
        }
    }

    private void drawHighlights(Canvas c, float indicatorStartX, float indicatorPosY,
                                int highlightPosition, float progress) {
        mPaint.setColor(colorActive);

        // width of item indicator including padding
        final float itemWidth = mIndicatorItemLength + mIndicatorItemPadding;

        if (progress == 0F) {
            // no swipe, draw a normal indicator
            float highlightStart = indicatorStartX + itemWidth * highlightPosition;

            c.drawCircle(highlightStart, indicatorPosY, mIndicatorItemLength / 2F, mPaint);

        } else {
            float highlightStart = indicatorStartX + itemWidth * highlightPosition;
            // calculate partial highlight
            float partialLength = mIndicatorItemLength * progress + mIndicatorItemPadding*progress;

            c.drawCircle(highlightStart + partialLength, indicatorPosY, mIndicatorItemLength / 2F, mPaint);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        outRect.bottom = mIndicatorHeight;
    }
}

非常感谢,LB Gupta快乐编码!!!!!

Answer 3

我复制了大卫•麦登杰克（David Medenjak）给出的相同答案，但是为了使圈子低于回收者的视野。我已经在上面的答案中更新了几行代码，请查看并相应使用。

/**
 * Created by shobhan on 4/10/17.
 */

public class CirclePagerIndicatorDecoration extends RecyclerView.ItemDecoration {

    private int colorActive = 0x727272;
    private int colorInactive = 0xF44336;

    private static final float DP = Resources.getSystem().getDisplayMetrics().density;

    /**
     * Height of the space the indicator takes up at the bottom of the view.
     */
    private final int mIndicatorHeight = (int) (DP * 16);

    /**
     * Indicator stroke width.
     */
    private final float mIndicatorStrokeWidth = DP * 2;

    /**
     * Indicator width.
     */
    private final float mIndicatorItemLength = DP * 16;
    /**
     * Padding between indicators.
     */
    private final float mIndicatorItemPadding = DP * 4;

    /**
     * Some more natural animation interpolation
     */
    private final Interpolator mInterpolator = new AccelerateDecelerateInterpolator();

    private final Paint mPaint = new Paint();

    public CirclePagerIndicatorDecoration() {
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(mIndicatorStrokeWidth);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setAntiAlias(true);
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        super.onDrawOver(c, parent, state);

        int itemCount = parent.getAdapter().getItemCount();

        // center horizontally, calculate width and subtract half from center
        float totalLength = mIndicatorItemLength * itemCount;
        float paddingBetweenItems = Math.max(0, itemCount - 1) * mIndicatorItemPadding;
        float indicatorTotalWidth = totalLength + paddingBetweenItems;
        float indicatorStartX = (parent.getWidth() - indicatorTotalWidth) / 2F;

        // center vertically in the allotted space
        float indicatorPosY = parent.getHeight() - mIndicatorHeight / 2F;

        drawInactiveIndicators(c, indicatorStartX, indicatorPosY, itemCount);


        // find active page (which should be highlighted)
        LinearLayoutManager layoutManager = (LinearLayoutManager) parent.getLayoutManager();
        int activePosition = layoutManager.findFirstVisibleItemPosition();
        if (activePosition == RecyclerView.NO_POSITION) {
            return;
        }

        // find offset of active page (if the user is scrolling)
        final View activeChild = layoutManager.findViewByPosition(activePosition);
        int left = activeChild.getLeft();
        int width = activeChild.getWidth();

        // on swipe the active item will be positioned from [-width, 0]
        // interpolate offset for smooth animation
        float progress = mInterpolator.getInterpolation(left * -1 / (float) width);

        drawHighlights(c, indicatorStartX, indicatorPosY, activePosition, progress, itemCount);
    }

    private void drawInactiveIndicators(Canvas c, float indicatorStartX, float indicatorPosY, int itemCount) {
        mPaint.setColor(Color.GRAY);

        // width of item indicator including padding
        final float itemWidth = mIndicatorItemLength + mIndicatorItemPadding;

        float start = indicatorStartX;
        for (int i = 0; i < itemCount; i++) {
            // draw the line for every item
            c.drawCircle(start + mIndicatorItemLength,indicatorPosY,itemWidth/6,mPaint);
          //  c.drawLine(start, indicatorPosY, start + mIndicatorItemLength, indicatorPosY, mPaint);
            start += itemWidth;
        }
    }

    private void drawHighlights(Canvas c, float indicatorStartX, float indicatorPosY,
                                int highlightPosition, float progress, int itemCount) {
        mPaint.setColor(Color.RED);

        // width of item indicator including padding
        final float itemWidth = mIndicatorItemLength + mIndicatorItemPadding;

        if (progress == 0F) {
            // no swipe, draw a normal indicator
            float highlightStart = indicatorStartX + itemWidth * highlightPosition;
         /*   c.drawLine(highlightStart, indicatorPosY,
                    highlightStart + mIndicatorItemLength, indicatorPosY, mPaint);
        */
            c.drawCircle(highlightStart,indicatorPosY,itemWidth/6,mPaint);

        } else {
            float highlightStart = indicatorStartX + itemWidth * highlightPosition;
            // calculate partial highlight
            float partialLength = mIndicatorItemLength * progress;
            c.drawCircle(highlightStart + mIndicatorItemLength,indicatorPosY,itemWidth/6,mPaint);

            // draw the cut off highlight
           /* c.drawLine(highlightStart + partialLength, indicatorPosY,
                    highlightStart + mIndicatorItemLength, indicatorPosY, mPaint);
*/
            // draw the highlight overlapping to the next item as well
           /* if (highlightPosition < itemCount - 1) {
                highlightStart += itemWidth;
                *//*c.drawLine(highlightStart, indicatorPosY,
                        highlightStart + partialLength, indicatorPosY, mPaint);*//*
                c.drawCircle(highlightStart ,indicatorPosY,itemWidth/4,mPaint);

            }*/
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        outRect.bottom = mIndicatorHeight;
    }
}

并将其应用于recyclerview，如下所示

//for horizontal scroll for recycler view 
 LinearLayoutManager linearLayoutManager
                = new LinearLayoutManager(context, LinearLayoutManager.HORIZONTAL, false);
recyclerview.setLayoutManager(linearLayoutManager);
recyclerview.addItemDecoration(new CirclePagerIndicatorDecoration());

Answer 4

如果有人需要，我为此编写了自己的库（经过大量搜索）：RecyclerView indicator。这是你如何做到的：

 <com.kingfisher.easyviewindicator.RecyclerViewIndicator
    android:id="@+id/circleIndicator"
    android:layout_width="match_parent"
    android:layout_height="20dp"
    app:avi_animation_enable="true"
    app:avi_drawable="@drawable/blue_radius"
    app:avi_drawable_unselected="@drawable/gray_radius"
    app:avi_height="10dp"
    app:avi_margin="10dp"
    app:avi_width="10dp"
    app:layout_constraintTop_toBottomOf="@+id/recyclerView">

</com.kingfisher.easyviewindicator.RecyclerViewIndicator>
// In code:
recyclerView.setAdapter(new TestAdapter());
recyclerViewIndicator.setRecyclerView(recyclerView);